The Brewers selected Fitzpatrick's contract from Triple-A Nashville on Wednesday.
Fitzpatrick had been off to a terrific start with Nashville, allowing just two unearned runs with an 11:2 K:BB over 10.1 innings. He'll receive his first call to the big leagues as a replacement in the Milwaukee bullpen for fellow left-hander Angel Zerpa (forearm), who was placed on the 15-day injured list.